MS Jet database engine

I have 10 workstations connected to an NT server. MS Access is loaded on each PC with the dbase on the server. All PC’s could access the dbase on the server. Yesterday, 2 PC’s only couldn’t access the dbase with the following error message “The Microsoft Jet database engine stopped the process becasue you and another user are attempting to change the same data at the same time” So far I’ve tried the following, rebooted the server, rebooted the PC’s, check permissions and reloaded MS Acess on the PC’s. The 2 workstations are still locked out. Anyone have any ideas?